Air displacement devices are used to increase the supply of air and fuel to internal combustion engines to boost engine horsepower. An example of an air displacement device is the “Roots blower” shown by P. H. Roots in U.S. Pat. No. 30,157 and G. Scheerer in U.S. Pat. No. 2,201,014. Each of these devices has a belt-driven shaft that drives two close-clearance rotors. The rotating rotors during each rotation sweep out a specific volume of air to an air receiver, such as an internal combustion engine. The rotational speed of the rotors largely determines the unthrottled volume of air discharged by the device to an air receiver.
C. N. Hansen and P. C. Cross in U.S. Pat. No. 6,241,498 disclose a supercharger having cooperating rotors drivably connected to an internal combustion engine for delivering an air/fuel mixture to the combustion chamber of the engine. The rotors have semi-cylindrical pockets and protrusions that continuously move air through the supercharger. The unthrottled volume of air delivered by the supercharger depends on the operating speed of the engine that drives the supercharger. The unthrottled volume of air delivered by the supercharger operating at a constant speed varies little. There are no air flow controls to regulate air flowing into and out of the supercharger.
J. E. Whitfield in U.S. Pat. No. 3,151,806 discloses a screw type compressor having a pair of rotors rotatably mounted on a housing. Volume control valves are located on the fluid inlet side of a fixed valve spacer. Compression control valves located on the fluid outlet side of the fixed valve spacer regulate the size and length of the fluid discharge outlet. Screws connected to the valves are used to adjust the positions of the valves to provide desired variations in fluid delivery volume and internal compression ratio.
F. Soderlund and K. Karlsson in U.S. Pat. No. 4,597,726 disclose a screw compressor having two rotors rotatably mounted on a housing for mutual meshing engagement. The pressure ratio and the capacity of the compressor is regulated with two slides mounted for independent axial movements. One slide regulates the capacity of the compressor. The other slide regulates the built-in volume ratio of the compressor.
N. Tsubol in U.S. Pat. No. 4,951,638 discloses a screw type supercharger having a pair of female and male rotors. Gears mounted on one end of each rotor synchronize rotation of the rotors so that they do not contact each other. One rotor is connected to an internal combustion engine which provides input power to the supercharger. The supercharger does not include intake air flow controls that regulate the volume of air delivered to an internal combustion engine intake manifold.
J. Oscarsson in U.S. Pat. No. 4,802,457 discloses an internal combustion engine equipped with a supercharger having rotors located in compression chambers. An air throttle device associated with the air inlet side of the supercharger is operated by the foot accelerator when the engine is only partially loaded to restrict the air flow into the rotor chamber.
A. B. Riach in U.S. Pat. No. 5,791,315 discloses a spark ignition internal combustion engine coupled to a supercharger having an air inlet port control for controlling the intake air into the supercharger. The control includes an inlet port valve which is open at full engine load and progressively closes when the engine load is progressively reduced and an air flow throttle valve which is open at full engine load and progressively closes when the load is progressively reduced.
G. Kirsten in U.S. Pat. No. 6,022,203 discloses a variable displacement screw-type compressor having a pair of rotors operable to move fluid under compression from an inlet channel to an outlet channel. Housing segments associated with the rotors control the internal compression ratio of the compressor. Control cams rotated with a stepper motor displace the housing segments against the bias of springs.
Four stroke engines do not require blowers or superchargers to supply air for starting and continuous operation. In a four stroke naturally aspirated or unboosted engine, the first down stroke of the piston draws air below atmospheric pressure into the cylinder. The air in the cylinder is compressed on the upstroke below the ignition temperature of the fuel. Fuel may be mixed with air prior to its induction into the cylinders or may be sprayed into the cylinders during the intake or compression strokes of the pistons. Near the top of the stroke of the pistons the air-fuel mixture is ignited by an electric are generated by spark plugs. The elevated pressure of the trapped gas due to the rapid burning of the fuel moves the pistons down during the working stroke. The subsequent upstroke of the pistons drives the exhaust gases and particulates out of the cylinders through exhaust valves to an exhaust manifold. The output torque of four stroke engines is controlled by varying the air mass and proportional fuel mass burned in each cylinder.